In the cosmetics field and in the medical field, there are commonly known containers inside which there is a fluid to be dispensed. The said fluid may be an anti-wrinkle solution, a fluid for the face or body, or products for the cosmetics and make-up market, such as foundation, lip gloss, liquid lipstick, mascara, concealer, primer for eyes, and primer for lips.
These containers are equipped with a cap for sealing.
In certain applications, in order to allow the extraction and the effective and localised use of the fluid from inside the bottle, the cap is associated with a dropper, which is equipped with an elastic element at the top thereof. When the elastic element is pressed, an overpressure is created inside the dropper (and in particular inside an element thereof called a pipette), which leads to the expulsion of the product contained within the pipette.
Upon releasing the pressure on the elastic element, a vacuum is created inside the pipette which, if the pipette is immersed in the fluid, allows the suction thereof into the pipette, thus preparing the fluid for a subsequent dispensing thereof.
Since the pipette is immersed in the fluid during use, the pipette is wet externally and may drip in an undesired manner during use, thus changing the dose of the product dispensed. This is not tolerable and therefore, in the most advanced systems, what is known as a ‘wiper’ is associated with the bottle opening, which cleans the exterior of the pipette simultaneously upon extraction thereof from the bottle.
In other applications, a stem is applied to the cap, with a semi-rigid element (called applicator) fastened to one end thereof, to concentrate the product in a particular position and allowing the localised application thereof.
Different applicator configurations allow different areas of application, with the possibility of diversifying the texture as well.
The wipers according to prior art are very simple and usually comprise a tubular element which is fastened, by interference fit, to a mouth of the container. Internally, the tubular element provides a passageway with a smaller section, which is sized according to the external dimension of the pipette. Therefore, when the pipette is moved within the passageway with a smaller section, the liquid present externally thereto stops on the wiper element, then falling back into the container.
The wiper devices according to prior art are made of plastic. When the said devices must be coupled to a plastic container, also made of injection blow moulded plastic or injection stretch blow moulded plastic, one simply has to carefully scale the coupling tolerance so as to obtain a good seal between the wiper element and the container and a stable, long-lasting positioning of the wiper within the container.
This is due to the fact that, during production of plastic containers with the technologies described above, the dimensional tolerance which can be achieved at the mouth of the container is very good, and therefore no further modifications are necessary in order to achieve secure fastening of the wiper device.
When, however, the container where the wiper is to be applied is made of glass or plastic shaped using the conventional blow moulding technique, the matter becomes more complicated, as the dimensional tolerances achieved when blowing glass and plastic are not as good as those achieved with the techniques discussed earlier.
As a result, it is not possible to fasten a wiper element stably using conventional methods to a blown glass or plastic container. Or rather, it is not possible to stably fasten a wiper to all glass or plastic containers originating from the same production batch.
This is because, in some containers, the mouth is wider than that ‘tolerated’ by the wiper element, and over time the wiper element tends to slide out of the container mouth. This is not acceptable because, as is known, the containers produced by blowing are destined for a high-end market, where product quality must remain at the maximum level over time.